Johannes Soulages

Microfluidic extensional rheometry using a hyperbolic contraction geometry

Microfluidic devices are ideally suited for the study of complex fluids undergoing large deformation rates in the absence of inertial complications. In particular, a microfluidic contraction geometry can be utilized to characterize the material response of complex fluids in an extensionally-dominated flow, but the mixed nature of the flow kinematics makes quantitative measurements of material functions such as the true extensional viscosity challenging. In this paper, we introduce the ‘extensional viscometer-rheometer-on-a-chip’ (EVROC), which is a hyperbolically-shaped contraction-expansion geometry fabricated using microfluidic technology for characterizing the importance of viscoelastic effects in an extensionally-dominated flow at large extension rates (

Reversible Switching of the Shear Modulus of Photoresponsive Liquid‐Crystalline Polymers

\lambda \dot \varepsilon _a \gg 1

Spatially resolved quantitative rheo-optics of complex fluids in a microfluidic device

, where

Preliminary Findings from the SHERE ISS Experiment

\lambda

Flow and Stability of Wormlike Micellar and Polymeric Solutions in Converging and T‐Shaped Microchannels

is the characteristic relaxation time, or for many industrial processes

Extensional Properties of a Dilute Polymer Solution Following Preshear in Microgravity

\dot \varepsilon _a \gg 1

Dynamics of Branched Polymer Melts in Complex Kinematics Flows: A Computational/Experimental Study

s

Investigating the stability of viscoelastic stagnation flows in T-shaped microchannels

^{-1}

Flow of branched polymer melts in a lubricated cross-slot channel: a combined computational and experimental study

). We combine measurements of the flow kinematics, the mechanical pressure drop across the contraction and spatially-resolved flow-induced birefringence to study a number of model rheological fluids, as well as several representative liquid consumer products, in order to assess the utility of EVROC as an extensional viscosity indexer.

Rapid viscoelastic switching of an ambient temperature range photo-responsive azobenzene side chain liquid crystal polymer

Manipulation makes light work: The morphology and rheological properties of a liquid-crystalline system can be dynamically manipulated with UV light by attaching photoresponsive liquid-crystalline moieties to a siloxane-based polymer. Stimulation with UV light induces a conformational change in the molecule, which disrupts the liquid-crystalline mesophase (see picture), and results in a dramatic change in its rheological properties.